1. Could.
2. Must.
3. Must not.
4. Could.
5. Must not.
6. Can.
7. Could, однако в этом случае я не уверена.
8. Could, can, can.
9. Must not, can.
10. Could not.
11. Must not.
16.A 17.B 18.B 19.A 20.C 21.C 22.B 23.A 24.C 25.A
You don't have to go to school on Sunday